Onward Technologies Inc Applications Engineer Interview Questions and Answers

Hashtable is synchronized while hashmap is not.

• Hashtable is thread-safe while hashmap is not.

• Hashtable does not allow null keys or values while hashmap allows one null key and multiple null values.

• Hashtable is slower than hashmap due to synchronization.

• Hashtable is a legacy class while hashmap is a newer implementation.

Hashmap is not thread-safe while Concurrent Hashmap is thread-safe.

• Hashmap is not suitable for multi-threaded environments as it can lead to race conditions and data inconsistencies.

• Concurrent Hashmap allows multiple threads to access and modify the map concurrently without any data inconsistencies.

• Concurrent Hashmap uses a technique called lock striping to achieve thread-safety.

• Concurrent Hashmap is slower than Hashma...read more

Convert given no to corresponding excel no.

• Excel no starts from 1 and goes up to 16384

• Excel no is calculated using column and row numbers

• For example, 1 corresponds to A, 27 corresponds to AA, 28 corresponds to AB, and so on

Find unique characters in a window of k size in a string.

• Use a sliding window approach.

• Maintain a hash table to keep track of character frequency.

• Remove characters from hash table as the window slides.